This invention relates to a method of forming a support structure on a base, and to a framework for use in forming such a support structure.
It is well known to form support structures such as roadways, canal or river or bank linings, mine packs, sea walls or the like from a material having a honeycomb structure, i.e. having a plurality of compartments or cells divided by dividing walls, each compartment or cell being filled with a suitable filler material. Examples of such materials for use in these support structures are HYSON-CELLS from MandS Technical Consultants and Services (Pty) Limited, GEOWEB from Presto Products Co., Tenweb from Tenax Corp, ARMATER from Crow Company, TERRACELL FROM Webtec Inc., ENVIROGRID from Akzo Nobel Geosynthetics Co. and GEOCELLS from Kaytech.
In making a support structure using these materials, it has generally been the practice for the walls of the compartments to be substantially planar, i.e flat, in use. This has lead to the result that the filler material, particularly when it is cement based, in certain circumstances shrinks away from the walls of the compartments during use of the support structure, thus creating gaps in the support structure and reducing any support of one compartment by adjacent compartments. This in turn results in the support structure not being able to take as great a load as may be desired.
There is thus need for a method of overcoming this problem.
According to a first aspect of the invention there is provided a method of forming a support structure on a base from a framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by dividing walls has a honeycomb structure, a wall or walls of each compartment including one or more hollow protrusions or one or more hollow recesses, or both, which method comprises the steps of:
(1) locating the framework on the base;
(2) filling the compartments with a filler material so that each compartment is adjacent to one or more other compartments filled with the filler material to support and be supported by the adjacent compartments, and so that each hollow protrusion in a compartment wall fills with the filler material so that each compartment protrudes into or is protruded into by at least one adjacent compartment so as to interlock adjacent compartments.
The protrusions or recesses must be of a size and shape to achieve interlocking of the filler material in one compartment with the filler material in an adjacent compartment, with the common wall between the compartment still separating the filler materials in the two compartments and thus acting as an expansion joint. In this way the overall strength of the support structure formed is increased, and there is also increased resistance against the filler material in one compartment being pushed or pulled out of that compartment.
The protrusion of one compartment into another adjacent compartment allows any load applied to the support structure to be transferred across the support structure, and thus assists in preventing fracture or disintegration of the support structure, which in turn allows the support structure to accept greater loads.
It is to be noted that a wall of a first compartment adjacent to a second compartment is also a wall of that second compartment, and thus that a protrusion in this wall of the first compartment equates to a recess in this wall of the second compartment.
As indicated above the protrusions or recesses may have any suitable shape, such as for example curved or rounded shapes, a dovetail shape, a T-shape, a block shape, or a pyramidal shape or the like.
For certain applications, where the support structure is intended to receive a load, the protrusions and recesses are curved or rounded so as to allow for a degree of rotation between adjacent compartments during filling and setting of the filler material, and to prevent any shearing of the protrusions from the remainder of the filler material in the relevant compartment on application of a load to the support structure.
When the protrusions and recesses are curved or rounded, each protrusion may be shaped substantially as a hemisphere or as a section of a sphere less than a hemisphere. In other words the protrusion may be approximately dome shaped. Alternatively, each protrusion may be shaped substantially as a semi cylinder or as a section of a cylinder less than a semi cylinder. Clearly, the recesses will have the complimentary shape.
In this case it is also important that the transition from the plane of the wall to the protrusion or recess be curved, again to prevent the shearing of the protrusion from the remainder of the filler material in the relevant compartment on application of a load.
A wall of a compartment may include one protrusion or recess, or may include two or more protrusions or two or more recesses, or a combination of protrusions and recesses.
Each compartment may have a single wall including a protrusion or a recess, or two or more or all of the walls including a protrusion or a recess.
Preferably, each wall of each compartment includes at least one protrusion or at least one recess.
The framework, i.e the tube and the dividing walls, may be made from any suitable flexible material. Although the material must possess some degree of flexibility, the degree of flexibility may range from very flexible up to semi rigid. The flexible material may be for example a plastics material such as for example a co-extruded or a biaxially extruded plastics material; a plastics laminate material such as for example a laminate of a plastics material and a metallic material or a textile material; a metallic material; a woven or non-woven textile material; a paper or cardboard material; and the like.
The flexible material is preferably a suitable plastics material.
The filler material may be any suitable filler material such as for example an inert filler material. e.g sand or gravel or the like, or a composition comprising a filler material and a settable binder therefor. Examples of such compositions include:
(i) an inert filler material such as sand or gravel or the like, and a cementitious binder, for example ordinary Portland Cement;
(ii) an inert filler material such as sand or gravel or the like and a bituminous binder;
(iii) a filler material such as soil treated with a suitable chemical composition such as calcium chloride, a lignin sulphonate or an ionic liquid to cause the soil to bind or set;
(iv) a filler material such as sand or gravel or the like and a resin binder, for example (a) a thermosetting resin such as polyurethanes and polyesters, (b) a thermoplastic resin such as polyethylene, EVA, or PVC, and (c) a suitable wax.
The settable composition may include a conventional foam or foaming agent so that the final set composition is a foamed composition, to reduce the weight thereof.
The filler material is preferably a fluid or paste which sets into a strong, rigid solid conforming to the geometry of the confining compartment walls.
The filler material preferably includes a binder such as a cementitious material, e.g the filler material may be a concrete material having a high slump value, in particular greater than 150, to which chemical additives have been added to aid setting.
The framework may have any suitable height and any suitable compartment size. For example, the height of the framework may range from 2 mm to 10 m inclusive, and each compartment may have a wall length of from 5 mm up to 2 m.
The compartments in the framework may have any suitable cross-section, such as square, hexagonal or octagonal, but preferably have a square cross-section. i.e each compartment is defined by four walls of substantially equal length.
The support structure may be made from a single framework as described above, or the support structure may be made from a plurality of frameworks laid side-by-side on the base, each framework being as described above and being filled with the filler material as described above. In this case, the compartments along an edge of a first framework will protrude into or be protruded into by the compartments along an adjacent edge of an adjacent framework, to interlock the frameworks one to another to form the support structure.
According to a second aspect of the invention there is provided a framework in use in forming a support structure on a base, the framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by dividing walls has a honeycomb structure, a wall or walls of each compartment including one or more hollow protrusions or one or more hollow recesses or both, so that, in use, when the compartments are filled with a filler material, each hollow protrusion in a compartment wall fills with the filler material so that each compartment protrudes into or is protruded into by at least one adjacent compartment to interlock adjacent compartments.